JPS6199560A - Method for maintaining constant outflow rate of molten metal in ladle - Google Patents

Abstract

PURPOSE:To maintain the specified outflow rate of a molten metal by evacuating the inside of a ladle when the height of the molten metal in the ladle is higher than a reference height and pressurizing the same when the height is lower than the reference height. CONSTITUTION:The optional height of the molten metal in the ladle is determined as the reference height and the height of the molten metal in the ladle during outflow is detected. The detected height and the reference height are compared and the molten metal is evacuated until both heights are made equal when the detected height is larger than the reference height. The molten metal is pressurized in the opposite case so that always specified outflow is executed. The degassing in the molten metal is executed by the evacuation.

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention relates to a method for keeping the outflow rate of molten metal in a ladle constant, for example, for producing metal powder, metal particles, etc. directly from molten metal. shot t i
The present invention relates to a method for keeping the outflow rate of molten metal in a ladle constant, which enables the molten metal used in the ng) method and injection method to be obtained from the ladle at a constant flow rate.

(Prior art) Conventionally, the conditions for producing metal powder, metal grains, etc. with good product yield and product quality from molten metal by, for example, the shotting method or the injection method are as follows: ■ Dissolved oxygen in the molten metal. 02, nitrogen N2, and hydrogen 1{2 are required to be sufficiently degassed, and (2) the flow rate of the molten metal is kept constant.

Of the conditions mentioned above, degassing in the molten metal is generally carried out at the stage of the ladle receiving the steel from the steelmaking furnace, by vacuum suction degassing, cancellation degassing by gas injection and stirring, or reflux degassing. This is done by law etc.

In addition, among the above conditions, the flow rate of the molten metal is kept constant by using a ladle with a handle or a small ladle, which is tilted to prevent slag from being mixed in, and the flow rate is adjusted manually. ,
In addition, using a clay pot-style ladle, it is suspended from above using a crane, etc., and its height is adjusted, while the rotation angle is adjusted using a handle, etc. using a rotation mechanism centered on a rotation axis slightly below the center of gravity. This is done by adjusting the outflow speed. However, these methods require a certain amount of space because the ladle must be tilted, and there are also safety issues.

Therefore, today, a bottom pouring ladle is generally used as a ladle, in which a stopper is disposed in a nozzle at the bottom, and the stopper is operated by a handle to cause molten metal to flow out from the nozzle.

(Problems to be Solved by the Invention) However, in the case of this bottom-pouring ladle, ■ The outflow speed of the molten metal is determined by the height of the molten metal in the ladle, and the outflow speed becomes too high in the initial stage of outflow. On the other hand, the flow rate becomes too small at the end of the outflow, making it difficult to adjust the flow rate. As mentioned above, it is difficult to adjust the flow rate, so metal powder of a certain quality is directly extracted from the molten metal by the shosotching method or the injection method. When trying to obtain metal particles, etc., the water jet speed must be adjusted, and the yield of the obtained products (metal powder, metal particles, etc.) is poor. When degassing is performed at the pot stage, there are problems such as the fact that degassing and flowing out of molten metal must be performed as separate processes, making the work at this stage complicated.

This invention was made in view of the above points, and it is possible to flow out molten metal at a constant flow rate regardless of the initial and final stages of the flow of molten metal, especially in a bottom pouring ladle. A method is provided for maintaining a constant outflow rate of molten metal in a ladle, which also allows for degassing within the metal.

(Means for Solving the Problems) This invention that solves the above-mentioned problems uses an arbitrary height of the molten metal in the ladle as a reference height, and when the height of the molten metal is higher than the reference height, reduces the pressure inside the ladle,
Further, when the height of the molten metal is lower than the reference height, the inside of the ladle is pressurized to keep the flow rate of the molten metal constant.

Here, as the ladle, a bottom pouring ladle is mainly used, but ladles of other configurations may also be used, and the ladle here refers to the entire container for receiving molten metal in a broad concept.
For example, it may be a pool of hot water.

Furthermore, the reason why the arbitrary height of the molten metal is used as the reference height is that the outflow velocity of the molten metal is determined by the height of the molten metal in the ladle according to Bernoulli's theorem. Setting the reference height also means setting an arbitrary outflow velocity as the reference velocity.

And the height of molten metal in the ladle is generally determined mechanically,
Although it is detected by electrical means, the outflow velocity V (not taking into account viscosity) of the molten metal at the height H to be detected is v = Cv7d7π where Cv is obtained by the velocity coefficient and has the unit The flow rate Q of molten metal from the nozzle per hour is q-caAh7 where C4 is the flow coefficient A is obtained from the cross-sectional area of the nozzle. It may also be possible to obtain the height.

In this case, the reference speed and the detected speed are compared, and the arbitrary height of the molten metal and the detected height are indirectly compared.

Further, the pressure reduction and pressurization are carried out by general means, and are carried out by changing the pressure in a time-series manner according to the changing height of the molten metal in the ladle.

That is, the height is changed continuously or intermittently depending on the detected height of the molten metal.

(Operation) Next, the operation of the present invention will be explained based on the above configuration.

The arbitrary height of the molten metal in the ladle is used as a reference cylinder, the height of the flowing molten metal inside the ladle is detected, the detected height and the arbitrary height are compared, and if the detected height is greater than the reference height The pressure is reduced until the heights are equal, and if the situation is reversed, the pressure is increased to ensure a constant outflow at all times. act to do.

(Example) Hereinafter, molten metal j
The present invention will be explained in more detail based on an example in which metal grains (shot grains) are directly produced from.

First, use a bottom pouring ladle as the ladle. The relationship between the height of the molten metal and the outflow velocity from the bottom pouring ladle is determined in advance by either theoretical or experimental values (in the case of molten metal, unlike water, its specific gravity is relatively high, so viscosity must be taken into account, so (experimental value) and set the arbitrary height of the molten metal in the ladle as the reference height.

Next, the molten metal tapped into the ladle from an electric furnace or the like is continuously flowed out from a nozzle and sprayed into water by a water jet to obtain metal grains (shot grains). Here, when the molten metal flows out, the height of the molten metal in the ladle is detected, the detected height and the reference height are compared, and if the detected height is greater than the reference height, the heights are equal. The pressure is reduced to 0□ oxygen and nitrogen N dissolved in the molten metal due to the reduced pressure.
2. Adjust the outflow rate while degassing hydrogen H2.

Next, the height of the molten metal in the ladle is detected, the detected height is compared with the reference height, and when the detected height is smaller than the reference height, the inside of the ladle is pressurized and the flow rate of the molten metal is reduced. After adjusting, all the specified molten metal flows out and becomes metal particles (shot particles).
get. Although pressurization was applied here, no adverse effect on degassing was observed.

According to this embodiment, the required size of metal grains (shot grains) can be obtained in yield.

-Experimental Example- Based on the above examples, experiments were conducted under the following conditions to confirm the effects.

Inner diameter 0.8m, height 2.50m, inner diameter of outflow hole 0.01
Using an 8 m bottom pouring ladle, an experiment was conducted on molten metal at a temperature of 1500° C., a carbon C content of 0.8%, and a specific gravity of 7.0, with the standard height of the molten metal in the ladle being 0.75 m.

The results are shown in Table 1.

- Comparative Example - In addition, in order to confirm the effect by comparing with the results of the experimental example, a conventional method (without pressure adjustment) was conducted under the same conditions as the experimental example.

The results are shown in Table 2.

Table 1 *1 Height of molten metal Table 2 f Also, to clarify the relationship between the above experimental examples and comparative examples, we also show the relationship between the adjusted pressure (mmHg) and the height of molten metal (m). A graph showing the relationship between the outflow velocity (m/s) of the molten metal and the height (m) of the molten metal is shown in FIG. 2.

-Comparison of product yield- Furthermore, in order to confirm the effects of the examples, metal particles (shot particle size: 2.8
A comparison of product yields was made for 3 to 0.297 mm.

The results are shown in Table 3.

Table 3 - Comparison of product quality - Further, in order to confirm the effects of the examples, product quality was compared using a life test and a cleaning force test based on the above-mentioned experimental example and comparative example. - [Comparison by Life Test] Product quality (number of shots) was compared by a life test under test conditions of 80% projection speed and 45% residual rate (55% breakdown method).

The results are shown in Table 4.

Table 4 (Number of projections) *l...Height of molten metal Note that 5240.5140 is the particle size according to JIS G 5903.

[Comparison by grinding test]

Projection speed: 67m/s Projection density: 90kg/m
2 test pieces: Comparison of product quality was conducted by abrasive test under test conditions of 5S41. The results are shown in Table 5.

Table 5 Rz surface roughness (μm) *1: Height of molten metal. Rz (10 point average roughness) is JIS B 06
According to 01.

From the results of comparisons of product yield δ and product quality based on the above experimental examples, comparative examples, experimental examples and comparative examples, the following was confirmed regarding the means of the examples.

■By reducing or pressurizing the molten metal, the flow rate can be made almost constant. This is because, in the case of the comparative example, there is a pressure difference in the molten metal applied to the outflow hole, and in the case of the experimental example, this pressure difference can be sufficiently adjusted. Moreover, this point can be confirmed from the graph shown in FIG.

■At the same time as keeping the outflow rate constant, degassing inside the molten metal can be sufficiently performed. In other words, 0 oxygen dissolved in the molten metal
2. Capable of degassing nitrogen N2 and hydrogen 11□. This point was confirmed by the fact that the life of the product (shot granules in the experimental example) was extended, the abrasive power of the shot granules increased, and the quality improved (see Table 4.5). On the other hand, comparative example, +7) Case/Another 1 degree 7
There is a point that it is difficult to stop the degassing process. Also,
Regarding the experimental samples, further improvement in quality was observed when the samples were further degassed in a separate process. In addition, in both the experimental example and the comparative example, degassing treatment was not performed in a separate process.

■Products with irregular shapes and low specific gravity are not often seen, and an improvement in product yield is observed (see Table 3). In addition, it was confirmed that the danger of steam explosion was eliminated, improving safety, and that waste heat could be used to dry short grains.

The above examples are for the case where metal grains (shot grains) are made directly from molten metal by the shotting method or injection method, but it goes without saying that the method can also be applied to casting of castings, etc. .

In addition, here, as shown in Figure 1, the pressure reduction and pressure were changed linearly as a function of the height of the molten metal.
Naturally, this may vary depending on the shape of the ladle, etc.

(Effects of the Invention) As is clear from the above description, according to the present invention, the molten metal can be flowed out at a constant flow rate regardless of the initial and final stages of the flow of the molten metal from the ladle, and moreover, the molten metal can be flowed out in parallel. A method can be provided for maintaining a constant outflow rate of molten metal in a ladle that also allows for degassing within the molten metal.

[Brief explanation of the drawing]

FIG. 1 shows the adjusted pressure (mmHg) in an embodiment of this invention.
) and the height of molten metal 'm),
FIG. 2 is a graph showing the relationship between the outflow velocity (m/s) of molten metal and the height (m) of molten metal in an embodiment of the present invention. Figure 1 Figure 2

Claims (3)

[Claims] (1) An arbitrary height of the molten metal in the ladle is set as the reference height, and when the height of the molten metal is higher than the reference height, the pressure inside the ladle is reduced, and the height of the molten metal is set as the reference height. A method for maintaining a constant outflow rate of molten metal in a ladle, characterized in that the outflow rate of molten metal in a ladle is kept constant by pressurizing the inside of the ladle when the outflow rate is lower than the height of the ladle. (2) The feature is that the molten metal in the ladle can be flowed out in a fixed amount by changing the amount of pressure reduction or the amount of pressurization in time series according to the height of the molten metal in the ladle. A method for maintaining a constant flow rate of molten metal in a ladle according to claim 1. (3) A method for keeping the flow rate of molten metal in the ladle constant according to claim (1) or (2), characterized in that a bottom pouring ladle is used as the ladle. Method.